leds: tca6507: Absorb platform data

The only in-tree usage of this driver is via device-tree. No on else
includes linux/leds-tca6507.h, so absorb the definition of platdata
structure.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Cc: NeilBrown <neilb@suse.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>